This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines may utilize cylinder liners or sleeves. Such internal combustion engines generally include an engine block having one or more cylinder bores. A piston is disposed within each cylinder bore when the internal combustion engine is fully assembled. Cylinder liners, which are generally cylindrical in shape, are positioned within the cylinder bore of the internal combustion engine between the piston and the engine block. Accordingly, the piston does not directly contact the engine block. Although cylinder liners often add complexity to the engine block, cylinder liners have some advantages. The cylinder liner presents a wear surface that can be replaced in the event of excessive wear. Excessive wear may occur in internal combustion engines that experience piston or ring failure. In such instances, the internal combustion engine can be more easily repaired without the need for re-boring and honing the engine block or replacing the engine block altogether. Cylinder liners can also be made from a different material than the material used in the engine block. Accordingly, the engine block can be made of a lighter, more brittle material such as aluminum to save weight, while the cylinder liner can be made of a heavier, stronger material such as cast iron to improve thermodynamics and durability.
One design problem that arises in internal combustion engines that utilize cylinder liners is how to effectively draw heat away from the cylinder liners. Cylinder liners are exposed to combustion and therefore are subject to high thermal loads. The cylinder liners themselves are relatively thin and often conduct heat better than the adjacent material of the engine block, making thermal management of the cylinder liner difficult. One solution to this problem is commonly referred to as a “wet liner” arrangement. In this arrangement, at least part of the cylinder liner is placed in direct contact with coolant water. The coolant water flows through a water jacket passageway disposed between at least a portion of the cylinder liner and the engine block. Thermal management is achieved more readily because heat from the cylinder liner is transferred directly to the coolant water. The coolant water in the water jacket passageway is replenished so that heat is continuously being drawn from the cylinder liner.
To increase heat transfer between the cylinder liner and the coolant water, several known designs call for cylinder liners with cut or cast-in grooves. While these designs do increase the surface area of the cylinder liner for improved cooling, the cut or cast-in grooves decrease the overall strength of the cylinder liner for any given liner wall thickness. Where the cylinder liner features cut grooves, the cutting operation removes material from the liner wall thereby weakening the cylinder liner. Where the cylinder liner features cast-in grooves, there is an absence of material adjacent the grooves (i.e. thinned areas in the liner wall). Accordingly, the cylinder liner is weak adjacent the grooves. Such cylinder liners sacrifice strength for cooling gains. As a result, these cylinder liners are more prone to deformation and failure during installation and operation of the internal combustion engine. Also, the compression ratio and maximum allowed engine speed (i.e. red-line rpms) of the internal combustion engine may have to be limited by the reduced strength of the cylinder liner.